1. Field of the Invention
The invention relates to a device and a method for joining the faces of parts with great longitudinal extension by friction welding. In particular, the invention relates to a device and a method for the axially aligned joining of rails and the like by friction welding.
2. Description of the Prior Art
Joining by welding is characterized according to DIN 1910 in that the cohesion of the parts is achieved through material fusion with the use of heat and/or force. The parting line between the workpieces is eliminated through the metallic bonding of their materials.
In friction welding, the surfaces of the workpieces or parts to be joined are moved relative to one another under pressure and the surface areas are heated through the friction, after which a positioning or pressing of the parts against one another occurs with metallic bonding of the same.
By means of friction welding chiefly parts having a rotationally symmetrical shape can be joined to one another or attached to workpieces, whereby at least one part is rotated about its axis, thus moved relative to the opposite part, and is positioned against a further part or workpiece under pressure.
Through the frictional heat released at the positioning surfaces, a heating of the surface areas occurs to a temperature at which the material of the part begins to soften. The actual welding results during the resting of the part(s) and an increased pressing of the positioning surfaces, a so-called bearing pressure, to obtain a secure metallic bonding of the materials.
Friction welded joints and devices for their production can have great importance and be very cost-effective for special materials and a joining of small or compact parts with a short time-consumption; however, with rods and the like with great longitudinal extension, a rotational movement of the same for the friction heating of the joint areas is often possible only with the greatest effort and, in many cases, only theoretically possible.
In particular with long rods with profiled cross section, such as, e.g., rails or beams, an axially aligned joining with alignment of the cross-sectional profile through friction welding does not seem cost-effective and cannot be produced with a necessary joint quality.
A method for joining railway tracks by friction welding is known from DE 198 07 457 A1 in which an intermediate piece is moved in linear or orbital oscillation between the rail ends to be connected. The two rail ends are thereby pressed toward one another onto the intermediate piece in the longitudinal direction of the rail in order to generate the heat necessary for welding through friction energy on both contact surfaces between each of the rail ends and each of the cut surfaces of the intermediate piece.
However, such a rail joint, which is expensive to produce, results in respectively two weld transitions that result in an increase of potential weak points that will possibly need to be tested extensively. Furthermore, guiding the temperature in the joint area during friction welding as well as system-dependent functional operations can be more difficult to control while maintaining quality.